Earlier this year, leaks from the White House indicated that computer viruses which targeted Iran's uranium enrichment facilities were the product of a joint American-Israeli cyber-espionage venture. Iran is said to be sinking under the weight of further cyberattacks aimed at its nuclear facilities and other parts of its critical infrastructure.

In July, Mikko Hypponen, the widely respected chief research officer of Finnish anti-virus company, F-Secure, received an email apparently from a scientist in Iran's Atomic Energy Organisation. In it, the scientist revealed that "our nuclear program has once again been compromised and attacked by a new worm with exploits which have shut down our automation network at Natanz and another facility Fordo near Qom". Even more bizarrely, he said the virus would order infected computers to play loud music in the middle of the night. "I believe it was playing Thunderstruck by AC/DC," he observed, with appropriate detachment.

To counter these multiple assaults, Iran has said it will take its computers offline, instead building an intranet that will function in Iran alone and not communicate with the outside world. This will represent a major step in the fragmentation of the internet into a series of giant intranets, each subject to the specific regulations of individual nation states. The move reduces Iran's risk of being infected by new viruses, though it will not eliminate it completely. But it would also be a devastating blow to ordinary Iranians, Iranian commerce and Iranian academics who keep abreast of global research through the net.

Some countries, such as China and Saudi Arabia, have already introduced extensive content control and surveillance of users. But the Iranian concept goes well beyond this. Taken to its conclusion, it would mean users could only access material from Iran that, presumably, had been approved by the authorities. "We have concerns from not only a human rights perspective, but about the integrity of the internet," David Baer, from the US state department, told the Washington Post this week. "When countries section off parts of the web, not only do their citizens suffer, everyone does."

An unregulated cyber-arms race in which states develop malicious code before deploying it across the world has been triggered. Recently the BKA, Germany's equivalent of the FBI, advertised openly for coders to write Trojan viruses for use in criminal investigations. "Governments, intelligence agencies and militaries are all doing this. Two years ago this would have been unacceptable," noted Hypponen, "but now everybody is at it." Two months ago the situation had become sufficiently grave to lure Jonathan Evans, the head of MI5, out of his traditional obscurity. "The extent of what's going on is astonishing with industrial scale processes involving many thousands of people" he said, pointing out that one British company had lost a staggering £800m as a consequence of a recent hack.

There is no framework for restricting the use of cyber-espionage tools or weaponry. Each government now argues that they have no option but to join the race or lose. And with no prospect of agreement between the US, China and Russia, the three most influential internet powers (and, indeed, cyber-weapons developers), the web is moving into choppy, unchartered waters.